A vehicle, such as an automobile, has a battery installed. Particularly, the inside of an engine room of a vehicle is affected by a temperature increase due to the engine or an environment, such as the season, and suffers a large temperature change, and hence it has been known that a battery installed in the engine room deteriorates or the battery becomes unstable in the performance. Thus, the battery is covered by a thermal insulating cover so that the effect of the ambient temperature on the battery is suppressed (see, for example, patent document 1).